Mesoscale Discussion 263

Issued

Mar 24, 2016, 7:53 AM CDT (12:53 UTC)

Expired

Mar 24, 2016, 10:30 AM CDT

In force

3 hr

Issued by

the Storm Prediction Center

Chance of a watch

40%

Counties Acadia Parish, LA, Allen Parish, LA, Avoyelles Parish, LA, Cameron Parish, LA, East Baton Rouge Parish, LA, East Feliciana Parish, LA, Evangeline Parish, LA, Iberia Parish, LA, Iberville Parish, LA, Jefferson Davis Parish, LA, Lafayette Parish, LA, Pointe Coupee Parish, LA, Rapides Parish, LA, Saint Landry Parish, LA, Saint Martin Parish, LA, St. Mary Parish, LA, Vermilion Parish, LA, West Baton Rouge Parish, LA, West Feliciana Parish, LA, Wilkinson County, MS

The Lake Charles radar (KLCH), 123 km from the middle of the area, began a volume at 12:53 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

194 
ACUS11 KWNS 241254
SWOMCD
SPC MCD 241253 
LAZ000-MSZ000-241530-

MESOSCALE DISCUSSION 0263
NWS STORM PREDICTION CENTER NORMAN OK
0753 AM CDT THU MAR 24 2016

AREAS AFFECTED...PORTIONS CENTRAL/SRN LA...SEWN MS.

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 241253Z - 241530Z

PROBABILITY OF WATCH ISSUANCE...40 PERCENT

SUMMARY...STRONGEST PART OF TSTM BAND THAT HAS PRODUCED SUB-SVR
GUSTS ACROSS SE TX IS FCST TO PROCEED EWD OVER MAINLY SRN LA...WITH
SOME INCREASE IN ORGANIZATION NOTED AND NWD EXTENSION POSSIBLE INTO
SLOWLY DESTABILIZING ENVIRONMENT PRECONVECTIVE WAA REGIME.  WW MAY
BE REQUIRED IF ADDITIONAL ORGANIZATION TAKES PLACE.

DISCUSSION...CLUSTER OF TSTMS THAT PRODUCED SVR GUSTS IN AUS AREA
AROUND 07Z SINCE BECAME MORE POORLY ORGANIZED...YET STILL
MAINTAINING SOME OF ITS ORIGINAL COLD POOL WHILE PRODUCING 30-45-KT
GUSTS ACROSS PORTIONS HOU METRO AND SURROUNDING TERRITORY.  THIS
ACTIVITY THEN FIRMED UP SOMEWHAT INTO SQUALL LINE THAT EXTENDED AT
1230Z FROM NEAR BKB SWWD ACROSS SABINE PASS REGION...BUT SINCE HAS
DISORGANIZED SLIGHTLY AGAIN.  

12Z LCH RAOB APPEARS TO HAVE SAMPLED IMMEDIATE PRECONVECTIVE
ENVIRONMENT REASONABLY WELL...WITH SFC DEW POINT 67 F AND 1.3-INCH
PW SUPPORTING AROUND 600 J/KG MLCAPE.  BUOYANCY DECREASES WITH NNEWD
EXTENT AHEAD OF SQUALL LINE...AND INCREASES SWD OVER GULF...LARGELY
COMMENSURATE WITH SFC THETAE.  BOUNDARY-LAYER MOIST ADVECTION AND
WAA JUST AHEAD OF THIS CONVECTION SHOULD MAINTAIN AT LEAST MRGLLY
UNSTABLE ENVIRONMENT.  MEANWHILE...BASE OF EML LAYER HAS BEEN LIFTED
AND WEAKENED...EVIDENT IN COMPARISON OF 00Z AND 12Z LCH RAOBS...AND
THAT PROCESS SHOULD CONTINUE IN NARROW ZONE JUST AHEAD OF CONVECTIVE
BAND.  THAT MAY BE RELATED PARTLY TO PASSAGE OF GRAVITY WAVE...
APPARENT FOR LAST FEW HOURS IN REFLECTIVITY ANIMATIONS AND
CONSISTENT SFC RESPONSES ABOUT 60-90 NM AHEAD OF CONVECTIVE BAND.

WINDS HAVE TEMPORARILY WEAKENED AND/OR VEERED IMMEDIATELY BEHIND
GRAVITY WAVE...AS SAMPLED BY THAT LCH RAOB AND BY EARLIER OBS. 
HOWEVER...SOME BACKING IS NOTED IN NARROW CORRIDOR BETWEEN THAT
PROCESS AND CONVECTIVE BAND.  ACCORDINGLY MODIFIED SOUNDING AND VWP
DOES RESULT IN LOCALLY ENHANCED LOW-LEVEL SHEAR AND HODOGRAPH
SIZES...DESPITE RATHER VEERED 850-MB FLOW...SUCH THAT 150-250 J/KG
0-1 KM SRH MAY BE AVAILABLE TO SOME PARTS OF CONVECTIVE BAND. 
50-50-KT EFFECTIVE-SHEAR MAGNITUDES ALSO ARE APPARENT OVER AREA.  AS
SUCH...SMALL/SHORT-LIVED TORNADO OR TWO CANNOT BE RULED OUT WITH
TRANSIENT MESO/MISO-CIRCULATIONS ALONG LEADING EDGE OF QLCS. 
HOWEVER...MAIN THREAT WILL BE DAMAGING GUSTS.  LIMITING FACTOR MAY
BE LACK OF MORE ROBUST INSTABILITY...WITH 
1.  ONLY LOW-MID-60S F DEW POINTS PRESENTLY APPARENT OVER MUCH OF
INLAND AREA NEAR/N OF I-10 FARTHER E...AND 
2.  DENSE CLOUD COVER PER VIS IMAGERY THAT WILL IMPEDE DIABATIC
HEATING.

..EDWARDS/DIAL.. 03/24/2016

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...JAN...LIX...LCH...SHV...

LAT...LON   29739367 30729299 31279251 31419206 31449093 30579081
            29809111 29259131 29419150 29379130 29519129 29519141
            29519150 29649158 29629165 29499178 29499188 29579207
            29539225 29599274 29779325 29739367

Mesoscale Discussions in Louisiana, 2016Mesoscale Discussions in Mississippi, 2016Every mesoscale discussion in 2016

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.